1. Field of the Invention
The present invention relates to a display device for the reproduction of characters and symbols including light sources in the form of incandescent lamps or lightbulbs, which are arranged in close proximity to each other on a substrate, and in particular, relates to a display device for moving illuminated writing, illuminated area or field, luminescent boards, marquees, or the like.
2. Discussion of the Prior Art
In general, display devices of the above-mentioned type are well known in actual practice, and serve for the reproduction or representation of characters or symbols; for example, such as letters, numerals, word signs, graphics and the like. For this purpose, numerous light sources in the form of incandescent lamps or lightbulbs are inserted on a common substrate or support in close proximity to each other. The substrate is utilized as a mounting plate and is equipped with lamp-holder sockets which are arranged in any suitable, preselectable pattern. Such sockets can be snapped into the mounting plate in conformance with the current state of the technology. However, they can also be fastened through other form-fitted or force-locking devices. The incandescent lamp is inserted from the front into the socket, whereas the electrical connections are displaced from the rear side of the mounting plate. The required reflector, as a rule, is slid forwardly onto the collar of the socket and receives a light distributing or diffusing cap, which can be configured to be either neutral or also colored. In front of the thusly equipped mounting plate, so as to provide a protective function, a surface-covering plexiglas plate, possibly of one continuous piece, is positioned in front of the light sources.
In this above-described construction, which is regularly employed in practice, it is disadvantageous that the reflector with the externally attached light distributing cap forms a closed chamber which is rapidly heated by the incandescent lamp or lightbulb. A dissipation of heat is only possible to a limited extent inasmuch as, on the one hand, the reflector and the lamp-holder socket are produced from a plastic material, and normally, an inadequate amount of fresh air flows into the space between the mounting plate and the front plate which is constituted of plexiglas. In order to be able to attain a dissipation of heat to an absolutely necessary extent, a blower is frequently employed, which blows the fresh air into the space between the mounting plate and the front plate. On the other hand, attempts have already been made in actual practice to provide the light distributing cap with a central bore which serves for the necessary heat dissipation. Were one to completely eliminate the light distributing cap, the legibility of the writing therebelow would suffer, and moreover, the reflectors would be rapidly dirtied, which would lead to a reduction in the efficiency or brightness of the light.
In addition thereto, the front or plexiglas face plate possesses the disadvantage that a reflective effect is unavoidable from a side viewing angle, and the ability to read from the side becomes basically poorer. Moreover, this plexiglas plate hinders the exchange of the incandescent lamps or lightbulbs.